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1.In bacteria, spores are not a reproductive phase as the name might indicate, but an extremely resistant form that the bacterium takes on in order to survive unfavorable conditions; it may be thought of as a dormant phase. Antibiotics act in different ways, but their purpose is to kill certain types of cells. Ironically, the use of some antibiotics can allows other, competitive bacterial species to profligate in the post-antibiotic environment. Because we haven't specified which type of antibiotic is being used, or what type of bacteria it is targeting, we can't say whether it will attack or ignore the Clostridium spores.

However, we can say that if the antibiotics target other bacterial flora, then Clostridium may awaken and lead to infection. If the antibiotics target the Clostridium, the Clostridium will die.

2.Clostridium is anaerobic, so it needs a non-oxygenated environment to thrive. It feeds in this environment until undergoing binary fission, as in many bacterial species, where the original cell splits into two genetically identical cells. The spore phase is not a reproductive phase.

3a. Bacteria can be modified through genetic engineering in a variety of ways, but one prominent example is the replacement of a bacterial gene for one which produces something useful from the human perspective, such as lactase or insulin.

3b & c. Viruses can be employed in genetic engineering to infect bacterial cells with the gene and restriction enzymes necessary to insert the modified gene into the bacterial genome, or to infect a multicellular organism with modified dna in a similar manner.